1. Field of the Invention:
This invention relates in general to systems for enhancing the capability of a pilot of a fighter type aircraft to withstand acceleration forces on his body.
2. Description of the Prior Art:
Pilots of high-performance jet fighter aircraft have always been prone to grayout or blackout, and to a lesser extent, loss of consciousness, due to the aircraft's high gravitational force (G-force) capability. Sharp high speed maneuvers can cause the gravitational forces to become very high in a short space of time. For example, a high performance fighter aircraft may be able to achieve 9-G's ( nine times the force of gravity) within three to four seconds time.
The only protection used in the past against this graying or blacking out is an anti-G suit and a straining maneuver performed by the pilot. The anti-G suit is a pair of trousers with a liner or bladder that can be inflated to more tightly squeeze the lower portion of the pilot's body from about the waist down. The suit will be connected to an air compressor through a valve. The inflated bladder helps keep blood from pooling in the lower extremities, which could result in grayout, blackout and loss of consciousness.
The valve is controlled by an accelerometer. The accelerometer is basically a weight and spring mechanism that will distend with increasing G-forces. The accelerometer is connected to the valve to inflate and deflate the suit accordingly. The anti-G suit inflates with increasing gravity forces to restrict the flow of blood to the pilot's lower extremities, so that oxygen carrying blood is available in the brain.
The response time in the suit is dependent on valve friction, the anti-G suit hose length, valve resistance, volume of the suit bladder, and the correctness of the fit of the suit. This response time causes a delay, typically about one-half to one second, between the pressure required and the actual pressure delivered.
This delay in pressure was not dangerously critical until the advent of aircraft capable of rapid-G onset and sustained high-G maneuvering. These characteristics cause the pilot to approach the G-induced loss of consciousness region without having the benefit of passing through the grayout region. The grayout region typically warns the pilot of the possibility of loss of consciousness or blackout. A properly fitted anti-G suit will raise the G-time tolerance for an increased protection of approximately one G. More importantly, it forces the pilot to begin his straining maneuver, which further increases his G-tolerance another three to four G's. The combination of these two functions allow the pilot to tolerate up to nine G's.
A rapid-G onset aircraft creates a need to shorten the anti-G suit inflation time delay and furnish the pilot pressure on his lower extremities so that he can better resist the G-load applied to his body. Some pilots have occasionally reached down and pre-inflated the anti-G suit with a test button prior to pulling G's if the time and conditions permitted. This action allows the pressure required in the suit to more closely match the pressure needed.